Self-Grounding I/O Card

ABSTRACT

A self-grounding input/output (I/O) card assembly in accordance with one embodiment of the present invention includes at least a printed circuit board (PCB), at least one BNC connector attached to the PCB, and a metallic tab formed on the PCB. In accordance with the present invention, the metallic tab is formed on the PCB such that when the I/O card assembly is installed into a metallic housing, the metallic tab contacts the metallic housing and bends back until the metallic tab makes contact with the body of the BNC connector thus creating a continuous grounding loop between the BNC connector, the self-grounding I/O card and the metallic housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 60/562,858, filed Apr. 15, 2004, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This invention relates to input/output (I/O) cards, and more particularly, to a self-grounding I/O card.

BACKGROUND ART

Transferring signals to and from printed circuit boards within an electronic device invariably involves printed circuit board connectors which couple signals to ribbon or wire conductors, coaxial cable etc. The ribbon, wire or coaxial conductors in turn couple the signals from the printed circuit board connector to and from a connection panel which provides an input output capability via conductors coupling to external equipment. Electronic equipment having such printed circuit boards and functioning with high frequency signals, for example in a range from 10 mega Hertz to beyond 1 giga Hertz, can suffer impaired performance. For example, if signal and signal return conductor impedance variations or discontinuities exist at each conductor junction, degraded signal propagation can result. Such impedance discontinuities, also known as return loss, will cause unwanted and undesirable signal reflections which degrade the wanted transmission signal by adding and or subtracting various components of the transmission signal and limiting the maximum interconnection length or signal detection threshold etc.

It is known to provide a direct connective arrangement between a printed circuit board conductor and a connector mounted to the printed circuit board such that when inserted within a module frame or chassis, the on-board connector protrudes beyond the module frame, or chassis to provide an I/O connection at a panel. In the case of a printed circuit board having BNC connectors, edge conductors are located at a module edge such that when inserted into a module frame the printed edge conductors extend or protrude into and mate with an end portion, or mounting throat of a bulkhead or chassis mounted BNC connector. This connective method offers the advantages of reduced parts count and reduced manufacturing and assembly costs. In addition this connective arrangement can provide a better impedance match between the BNC connector and the PCB conductor.

A BNC mounting throat, however, requires excellent contact performance for both, the signal and signal return or ground connections to reduce the effects of electromagnetic radiation. Electromagnetic radiation is a natural consequence of current flow through the electrical circuits on a card. Unchecked, electromagnetic radiation can interfere with and disrupt the operation of electrical and electronic circuits in a host device. The interference resulting from electromagnetic radiation is commonly known as electromagnetic interference (EMI). Because electromagnetic radiation is a natural consequence of current flow, it cannot practically be prevented. Instead, emissions of the electromagnetic radiation must be controlled in order to prevent harmful EMI from resulting.

In many circumstances, electromagnetic interference (EMI) can be prevented or reduced by enclosing components in a substantially continuous conductive shell. That is, it is generally acknowledged that metal or metallic structures, if properly located and grounded, can be effective in controlling harmful electromagnetic radiation. Metals are effective in this regard because they generally have a low characteristic impedance which has the desirable characteristic of reflecting the high impedance electromagnetic radiation typically emitted by computers and related devices. By reflecting the electromagnetic radiation away from vulnerable circuits or devices, the metal thereby acts as a protective shield.

In prior art arrangements to prevent harmful EMI from resulting, return signal connection spring ground clips have been employed, which are attached to a BNC body, as shown in FIGS. 1A and 1B. However this BNC to PCB signal grounding arrangement proves unreliable during multiple insertion and removal cycles. Frequently collisions occurred between the printed circuit board edge and the spring grounding clips causing bending or mechanical deformation. At best the return loss of the connective junction is compromised but more frequently the mechanical damage is such to prevent module insertion and occasionally resulting in signal conductor short circuits. Such spring clip damage is not easily repairable, and requires that the equipment chassis is un-cabled and mechanically disassembled to allow the repair of the hard mounted grounding clips attached to the BNC connectors at chassis rear panel. In addition, many prior art grounding arrangements, such as the grounding arrangement described above, limit the number of I/O connections able to be provided at a panel of a chassis, such as a rack unit, housing an I/O card because of the space requirements of such grounding methods. That is, in prior art grounding methods the proximity of I/O connectors is limited by the space requirements of such grounding methods.

BRIEF SUMMARY OF THE INVENTION

The present invention addresses the deficiencies of the prior art by providing a self-grounding input/output (I/O) card.

In one embodiment of the present invention, a self-grounding input/output (I/O) card assembly includes a printed circuit board (PCB), at least one metallic I/O connector (such as a BNC) attached to the PCB board, and a metallic tab formed on the PCB. In accordance with the present invention, the metallic tab is formed on the PCB such that when the self-grounding I/O card is installed into a metallic housing, the metallic tab formed on the PCB contacts the metallic housing and bends back until the metallic tab makes contact with the body of the metallic I/O connector (e.g., BNC) thus creating a continuous grounding loop between the metallic I/O connector (e.g., BNC), the self-grounding I/O card and the metallic housing.

In an alternate embodiment of the present invention, a self-grounding input/output (I/O) card as described above further includes a slot for mating said I/O card with a second PCB. The slot of the self-grounding I/O card of the present invention is lined with solder to facilitate a continuous grounding loop including the second PCB.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:

FIG. 1A depicts a prior art connector signal grounding arrangement where spring contacts are arranged in two pairs which are shared between adjacent connectors;

FIG. 1B depicts a second prior art connector signal grounding arrangement which is also arranged in pairs disposed between adjacent bulkhead connector bodies;

FIG. 2 depicts a high level diagram of a self-grounding I/O card in accordance with one embodiment of the present invention; and

FIG. 3 depicts a high level diagram of a self-grounding I/O card in accordance with an alternate embodiment of the present invention.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.

DETAILED DESCRIPTION

The present invention advantageously provides a self-grounding input/output (I/O) card. Although throughout the teachings herein and in various embodiments of the present invention, the aspects of the present invention are described with respect to an I/O card housed by a rack unit and including a BNC I/O connector, the specific embodiments of the present invention should not be treated as limiting the scope of the invention. It will be appreciated by those skilled in the art and informed by the teachings of the present invention that the concepts of the present invention can be advantageously applied to I/O cards housed in substantially any chassis and comprising substantially any metallic I/O connector.

The prior signal grounding arrangement shown FIGS. 1A and 1B offer the benefits of reduced parts count and reduced manufacturing and assembly costs. More specifically, FIG. 1A depicts a prior art connector signal grounding arrangement where spring contacts are arranged in two pairs which are shared between adjacent connectors. The spring contacts extend beyond the body of the BNC connector and are formed to accept a PCB edge connector. Similarly, FIG. 1B depicts a second prior art connector signal grounding arrangement which is also arranged in pairs disposed between adjacent bulkhead connector bodies.

However, the return signal grounding arrangements of FIGS. 1A and 1B suffer unreliability during module insertion and removal cycles. Module misalignment during insertion of the PCB edge connector into the hard mounted BNC grounding springs results in collisions with the grounding springs causing bending or mechanical deformation. Frequently bent spring clips block PCB module insertion into the BNC throat and thus render the equipment inoperative. Furthermore such damage is not repairable from the chassis front and requires the chassis to be un-cabled and removed for mechanical repair. In addition, the return signal grounding arrangements of FIGS. 1A and 1B require large spacing between the BNC connectors and limit how close I/O cards can be placed to one another.

FIG. 2 depicts a high level diagram of a self-grounding I/O card in accordance with one embodiment of the present invention. The self-grounding I/O card 200 of FIG. 2 illustratively comprises a printed circuit board (PCB) 210 and metallic PCB edge I/O connectors (illustratively two BNC connectors) 222 and 224, mounted onto the edge of the PCB 210 using any of the methods known in the art for mounting connectors onto PCB's. The self-grounding I/O card 200 of FIG. 2 further comprises a respective tab 232 and 234 formed along the edge of the PCB 210 for each of the metallic I/O connectors 222 and 224. The tabs 232 and 234 formed along the edge of the PCB 210 are metallic. For example, in one embodiment of a self-grounding I/O card in accordance with the present invention, the tabs formed along the edge of the PCB are solder-plated. In alternate embodiments of a self-grounding I/O card in accordance with the present invention, the tabs formed along the edge of the PCB are formed or plated out of other metallic materials such as steel, tin or other conductive metallic composites. Although in FIG. 2, the self-grounding I/O card illustratively comprises two metallic edge I/O connectors 222, 224 and two respective metallic tabs 232, 234, alternate embodiments of a self-grounding I/O card in accordance with the present invention may comprise any number of metallic edge I/O connectors and respective metallic tabs.

In accordance with the present invention, when a self-grounding I/O card of the present invention, such as the I/O card 200 of FIG. 2, is installed into a metal chassis (not shown) for housing the I/O card 200, each metallic tab 232, 234 contacts a metal rear panel of the chassis and bends back until the tabs 232, 234 make contact with the body of the respective metallic edge I/O connectors 222, 224, thus creating a continuous grounding loop from the metallic edge I/O connectors 222, 224 to the chassis (not shown). The continuous grounding loop created when the tabs 232, 234 make contact with the body of the metallic edge I/O connectors 222, 224 and with a panel of a metallic chassis that houses the self-grounding I/O card 200, reduces or completely prevents electromagnetic interference (EMI).

Optionally, a protruding edge of the metallic tabs of a self-grounding I/O card of the present invention may mate with a hole or indentation having a similar form in for example a metal rear panel of a chassis that houses the self-grounding I/O card for not only completing a continuous grounding loop from the metallic edge I/O connectors to the chassis and for grounding the I/O card itself, but also for assisting in locating the self-grounding I/O card of the present invention and for providing stability to the self-grounding I/O card. For example, in the self-grounding I/O card 200 of FIG. 2, the outer-most protruding edge of the tabs 232, 234 (illustratively depicted as substantially rectangular) mate with a substantially rectangular hole or indentation of a metal rear panel of a chassis (not shown) that houses the self-grounding I/O card 200 of FIG. 2, for completing a continuous grounding loop from the metallic edge I/O connectors to the chassis, for grounding the I/O card itself and for providing stability to the self-grounding I/O card 200. That is, when at least a portion of the metallic tabs of a self-grounding I/O card of the present invention mate with an indentation or hole of a housing, the located metal tabs provide support for the I/O card when an exterior connector is being mated with the metallic edge I/O connectors of the I/O card. For example, in the case of BNC connectors, the located metal tabs provide support for the I/O card when an exterior connector is being mated with the BNC connectors of the I/O card which requires a twisting motion.

FIG. 3 depicts a high level diagram of a self-grounding I/O card in accordance with an alternate embodiment of the present invention. The self-grounding I/O card 300 of FIG. 3 illustratively comprises substantially the same components as the self-grounding I/O card 200 of FIG. 2, however, the self-grounding I/O card 300 of FIG. 3 further comprises a slot for inventively mating with another PCB card (described in greater detail below).

More specifically, the self-grounding I/O card 300 of FIG. 3 illustratively comprises a printed circuit board (PCB) 310 and metallic PCB edge I/O connectors (illustratively two BNC connectors) 322 and 324, mounted onto the edge of the PCB 310 using any of the methods known in the art for mounting connectors onto PCB's. The self-grounding I/O card 300 of FIG. 3 further comprises a respective tab 332 and 334 formed along the edge of the PCB 310 for each of the metallic I/O connectors 322 and 324. The tabs 332 and 234 formed along the edge of the PCB 310 are metallic. For example, in one embodiment of a self-grounding I/O card in accordance with the present invention, the tabs formed along the edge of the PCB are solder-plated. In alternate embodiments of a self-grounding I/O card in accordance with the present invention, the tabs formed along the edge of the PCB are formed or plated out of other metallic materials such as steel, tin or other conductive metallic composites. Although in FIG. 3, the self-grounding I/O card illustratively comprises two metallic edge I/O connectors 322, 324 and two respective metallic tabs 332, 334, alternate embodiments of a self-grounding I/O card in accordance with the present invention may comprise any number of metallic edge I/O connectors and respective metallic tabs.

As recited above with respect to the self-grounding I/O card 200 of FIG. 2, when the self-grounding I/O card 300 of FIG. 3, is installed into a metal chassis (not shown) for housing the I/O card 300, each metallic tab 332, 334 contacts a metal rear panel of the chassis and bends back until the tabs 332, 334 make contact with the body of the respective metallic edge I/O connectors 322, 324, thus creating a continuous grounding loop from the metallic edge I/O connectors 322, 324 to the chassis (not shown). The continuous grounding loop created when the tabs 332, 334 make contact with the body of the metallic edge I/O connectors 322, 224 and with a panel of a metallic chassis that houses the self-grounding I/O card 300, reduces or completely prevents electromagnetic interference (EMI).

As described above, the self-grounding I/O card 300 of FIG. 3 further comprises a slot 350. The slot 350 comprises a cut-out in the PCB 310 completely metallically lined for mating with another PCB card (not shown). For example, if the self-grounding I/O card 300 of FIG. 3 were configured as an audio/video I/O card to be installed in, for example, an audio/video router, the slot 350 of the self-grounding I/O card 300 may be adapted to mate with a motherboard (e.g., backplane, matrix board or switch board) of the audio/video router to at least create a continuous grounding loop that includes the audio/video router motherboard. The details of such the arrangement of such an inventive audio/video router are described and claimed in a commonly assigned patent application entitled “Improved I/O Cards and Card Arrangements for I/O Devices”, filed simultaneously herewith, the teachings of which are incorporated herein by reference in their entirety. More specifically, in an improved I/O card arrangement for I/O devices in accordance with the invention, a self-grounding I/O card of the present invention, such as the self-grounding I/O card 300 of FIG. 3, includes a slot 350 for mating with a slot or metallic strip of a second PCB card such that the metallic, edge I/O connectors 322, 324 of the I/O card 300 straddle an I/O connector of the second PCB card, the inventive arrangement of which enables more input and output audio and video connections and connectors to be provided by the inventive I/O device and provides a continuous grounding loop for the device.

More specifically, the slot 350 of the self-grounding I/O card 300 of FIG. 3 is metallically lined. For example, in one embodiment of a self-grounding I/O card in accordance with the present invention, the slot formed in the PCB is solder-plated. In alternate embodiments of a self-grounding I/O card in accordance with the present invention, the slot formed in the PCB is lined with other metallic materials such as steel, tin or other conductive metallic composites. The PCB card (e.g., motherboard card, matrix card, switch card, etc.) to be mated with the self-grounding I/O card 300 may similarly comprise a metallically lined slot, or alternatively a metallic strip, that mates with the metallically lined slot 350 of the I/O card 300 of the present invention, such that a continuous grounding loop is formed including at least the metallic edge I/O connectors 322, 324 of the self-grounding I/O card 300, the self-grounding I/O card 300, the mated PCB card and a metallic chassis that houses the self-grounding I/O card 300 and the mated PCB card. The continuous grounding loop created reduces or completely prevents electromagnetic interference (EMI) for a device including the self-grounding I/O card 300 and the mated PCB card.

Although the concepts of a self-grounding I/O card of the present invention described above with reference to FIG. 3 were described as mating with a matrix card, etc., it will be appreciated by those skilled in the art and informed by the concepts of the present invention, that a self-grounding I/O card of the present invention may be adapted to mate with substantially any other PCB card such that a continuous grounding loop is facilitated between at least the self-grounding I/O card of the present invention and the mated PCB card. It should further be understood that the self-grounding I/O card of the present invention further facilitates a continuous grounding loop between any metallic connectors included on the self-grounding I/O card, the self-grounding I/O card itself, any mated PCB boards, mated as described above, and a metallic housing.

While the forgoing is directed to various embodiments of the present invention, other and further embodiments of the invention can be devised without departing from the basic scope thereof. As such, the appropriate scope of the invention is to be determined according to the claims, which follow. 

1. An input/output (I/O) card assembly, comprising: a printed circuit board (PCB); at least one metallic I/O connector attached to said PCB; and a metallic tab formed on said PCB, said metallic tab formed such that when said I/O card assembly is installed into a metallic housing, said metallic tab contacts said metallic housing and bends back until the metallic tab makes contact with the body of said at least one metallic I/O connector thus creating a continuous grounding loop between said at least one metallic I/O connector, said I/O card assembly and said metallic housing.
 2. The I/O card assembly of claim 1, wherein said at least one metallic I/O connector comprises at least one BNC connector.
 3. The I/O card assembly of claim 1, wherein said metallic tab comprises solder.
 4. The I/O card assembly of claim 1, further comprising a slot for mating said I/O card assembly with a second PCB.
 5. The I/O card assembly of claim 4, wherein said slot is metallically lined.
 6. The I/O card assembly of claim 5, wherein said slot is lined with solder.
 7. The I/O card assembly of claim 4, wherein said I/O card assembly comprises an audio/video card.
 8. The I/O card assembly of claim 7, wherein said second PCB comprises a matrix PCB having a metallically lined slot.
 9. The I/O card assembly of claim 1, wherein at least a portion of said at least one metallic tab mates with a similarly shaped indentation or hole of said metallic housing for providing support for said I/O card assembly. 